Sand flies: Basic information on the vectors of leishmaniasis and their interactions with Leishmania parasites

Abstract

Blood-sucking arthropods transmit a variety of human pathogens acting as disseminators of the so-called vector-borne diseases. Leishmaniasis is a spectrum of diseases caused by different Leishmania species, transmitted quasi worldwide by sand flies. However, whereas many laboratories focus on the disease(s) and etiological agents, considerably less study the respective vectors. In fact, information on sand flies is neither abundant nor easy to find; aspects including basic biology, ecology, and sand-fly-Leishmania interactions are usually reported separately. Here, we compile elemental information on sand flies, in the context of leishmaniasis. We discuss the biology, distribution, and life cycle, the blood-feeding process, and the Leishmania-sand fly interactions that govern parasite transmission. Additionally, we highlight some outstanding questions that need to be answered for the complete understanding of parasite–vector–host interactions in leishmaniasis.

Leishmania Vaccines: the Current Situation with Its Promising Aspect for the Future

“…The production of IFN-γ by CD4+ T cells activates macrophages to kill parasites under nitric oxide (NO)-mediated conditions [23]. Disease progression is largely driven by the production of non-protective IL-4-driven Th2-associated cytokines IL-4, IL-10, IL-13, and TGF-β [24][25][26]. Some species, such as L. mexicana and L. amazonensis in the New World, unlike L. major, can survive in conditions of limited Th1 immune responses in the host [27].…”

Data-Driven Predictions of Potential Leishmania Vectors in Latin America

“…Past vector identification has typically relied on the following criteria stated by Killick-Kendrick: (i) epidemiological observation that the sandfly is anthropophilic, (ii) proof that the fly feeds regularly on a relevant reservoir host, (iii) repeated isolation and identification of the same species of Leishmania spp. promastigotes infecting the humans in the surrounding area, (iv) evidence that the fly supports the complete development of the parasite, (v) and experimental evidence the sandfly can transmit the parasite through blood meal bite [17][18][19]. We defined a known vector to be a sandfly that is incriminated as a Leishmania vector by these criteria, which are generally considered to be the gold-standard for identification [18].…”

“…Parasite-vector interactions can be divided into restrictive (sandflies that demonstrate specificity for the Leishmania species they can transmit) and permissive (sandflies that show non-specific interactions) groupings under laboratory conditions [17]. While restrictive pairs are well studied and linked together using molecular analysis methods, not much is known about permissive interactions, and they may be under-represented in the known list of sandfly vectors [17]. Thus, the current classification criteria might overlook some sandfly vectors that carry several different species of Leishmania .…”

Total RNA sequencing of Phlebotomus chinensis sandflies in China revealed viral, bacterial, and eukaryotic microbes potentially pathogenic to humans

“…Sandflies (Order Diptera, Subfamily Phlebotominae) are flying, piecing, and blood-sucking vectors well known for transmitting diseases such as leishmaniasis [ 5 ] and pappataci fever [ 6 ]. The former was caused by a eukaryotic microbe Leishmania endemic in over 90 countries and causing > 50,000 deaths per year across the globe [ 7 ], whereas the latter was caused by members of the genus Phleboviruses mainly reported in countries along the Mediterranean coast [ 6 ].…”